Re: RE: Re: DML Reason for 3.55 to 3.90 swap.

From: Gary Shook (gary.shook@mci.com)
Date: Mon Jan 04 1999 - 14:52:15 EST


The best advice that I have is to get a good transmission temp gauge... heat
is the #1 killer of transmissions, and a rise in temp will tell you when the
trans has started to slip, so you can take steps (out of OD & slow down in
short term, add cooler long term) to cool it. If you're going to tow alot,
especially in hilly areas & altitude, you should REALLY have one..

>Towing in OD will eventually hose your transmission and will happen sooner
>if it hunts for gears. Nothing controversial about it. My guess is that
>you'll pay allot for the gear swap then later a lot more for your
>transmission rebuild. The higher the R's the more power you have at to
punch
>it and pass the slow person in the fast lane.
>
<snip>
The other thing that happens when towing in OD is that when the RPMs are
lower, the pump pressure is lower, Which can result in poor lubrication when
you need it most. I have the 3.92's in my Ram with 32" tires, and can tow ~
5000Lbs in OD on FLAT roads... as soon as I get to a hill, I slow it down &
turn OD off- I'd rather bring the RPMs up than risk losing the tranny... I
don't have a tranny temp gauge, because I don't tow very much (less than 5%
of the time- more like 1%)

>The reason that I want to switch to the 3.90's is to increase the pulling
>power, and raise my highway RPM's a bit when towing in O/D. I just bought
a
>high-po jetboat on a tamdem trailer (about 2500# total), which I plan to
>pull a lot this summer, and I figure that the 3.90's will cause less stress
on
>the O/D unit. Do you other guys tow in O/D? I know this is a
controversial
>subject, but I can't bear to watch the RPM's if I take it out of O/D at
>interstate speeds.
I don't know the terrain you're towing on, tire size... and I'd be willing
to bet that a Jetboat & tandem trailer is more than 2500#... I'd look
further into that..

I also don't know whether you've got 4x4 or not... sometimes pulling a boat
out of the water is tough without it... make sure you at least have a LSD..

Good luck,

Gary Shook



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